1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device including an oxide semiconductor, a method of manufacturing an oxide, or a method of testing an oxide.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a power storage device, an imaging device, a memory device, a processor, an electronic device, a method for driving any of them, a method for manufacturing any of them, and a method for testing any of them.
2. Description of the Related Art
In recent years, display devices have been used in various electronic devices such as television receivers, personal computer monitors, and smart phones, and the performance of the display devices has been improved to achieve higher definition, lower power consumption, and other various objectives.
In addition, semiconductor devices such as central processing units (CPUs), memories, and sensors have been used in various electronic devices such as personal computers, smart phones, and digital cameras. The performance of the semiconductor devices has also been improved to achieve miniaturization, lower power consumption, and other various objectives.
One of the ways that have been proposed to achieve higher performance such as higher definition, lower power consumption, and miniaturization is the use of an oxide semiconductor for a semiconductor layer (hereinafter also referred to as an active layer, a channel layer, or a channel formation region) of a transistor in a semiconductor device. An example of the transistor includes an oxide of indium, gallium, and zinc (hereinafter also referred to as an In—Ga—Zn oxide) for a channel layer (see Patent Document 4).
In particular, a transistor using an oxide semiconductor in a channel layer is used as a switching element or the like in a display device (Patent Documents 1 and 2).
Oxide semiconductors have been researched since early times. In 1988, there was a disclosure of a crystal In—Ga—Zn oxide that can be used for a semiconductor element (see Patent Document 3).
In 2013, it is reported that an amorphous In—Ga—Zn oxide whose crystallization is promoted by irradiation with an electron beam has an unstable structure and that the formed amorphous In—Ga—Zn oxide has no ordering in observation with a high-resolution transmission electron microscope (see Non-Patent Document 1).
In 2014, electric characteristics and reliability of a transistor using an amorphous In—Sn—Zn oxide were reported (see Non-Patent Document 6). It was reported that, in the transistor using an amorphous In—Sn—Zn oxide, electrons accelerated by an electric field generated inside the oxide form a plurality of carriers because of impact ionization, which leads to deterioration with an increase in drain current.
In 2014, it was also reported that a transistor including a crystalline In—Ga—Zn oxide has more excellent electrical characteristics and higher reliability than a transistor including an amorphous In—Ga—Zn oxide (see Non-Patent Documents 2 to 4). These documents report that a crystal boundary is not clearly observed in an In—Ga—Zn oxide including a c-axis aligned a-b-plane-anchored crystalline oxide semiconductor (CAAC-OS).
As a kind of a structure of polymer crystal, a concept of “paracrystal” is known. A paracrystal seemingly has a trace of crystal lattice; however, compared with an ideal single crystal, the paracrystal has a distorted crystal structure (see Non-Patent Document 5).